KVM: MMU: cache mmio info on page fault path
If the page fault is caused by mmio, we can cache the mmio info, later, we do
not need to walk guest page table and quickly know it is a mmio fault while we
emulate the mmio instruction
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 59086a7..8da1400 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -424,6 +424,11 @@
u64 mcg_ctl;
u64 *mce_banks;
+ /* Cache MMIO info */
+ u64 mmio_gva;
+ unsigned access;
+ gfn_t mmio_gfn;
+
/* used for guest single stepping over the given code position */
unsigned long singlestep_rip;
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 02c839f..d1986b7 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -217,11 +217,6 @@
}
EXPORT_SYMBOL_GPL(kvm_mmu_set_mask_ptes);
-static bool is_write_protection(struct kvm_vcpu *vcpu)
-{
- return kvm_read_cr0_bits(vcpu, X86_CR0_WP);
-}
-
static int is_cpuid_PSE36(void)
{
return 1;
@@ -243,11 +238,6 @@
return pte & PT_PAGE_SIZE_MASK;
}
-static int is_writable_pte(unsigned long pte)
-{
- return pte & PT_WRITABLE_MASK;
-}
-
static int is_dirty_gpte(unsigned long pte)
{
return pte & PT_DIRTY_MASK;
@@ -2247,15 +2237,17 @@
send_sig_info(SIGBUS, &info, tsk);
}
-static int kvm_handle_bad_page(struct kvm *kvm, gfn_t gfn, pfn_t pfn)
+static int kvm_handle_bad_page(struct kvm_vcpu *vcpu, gva_t gva,
+ unsigned access, gfn_t gfn, pfn_t pfn)
{
kvm_release_pfn_clean(pfn);
if (is_hwpoison_pfn(pfn)) {
- kvm_send_hwpoison_signal(gfn_to_hva(kvm, gfn), current);
+ kvm_send_hwpoison_signal(gfn_to_hva(vcpu->kvm, gfn), current);
return 0;
} else if (is_fault_pfn(pfn))
return -EFAULT;
+ vcpu_cache_mmio_info(vcpu, gva, gfn, access);
return 1;
}
@@ -2337,7 +2329,7 @@
/* mmio */
if (is_error_pfn(pfn))
- return kvm_handle_bad_page(vcpu->kvm, gfn, pfn);
+ return kvm_handle_bad_page(vcpu, v, ACC_ALL, gfn, pfn);
spin_lock(&vcpu->kvm->mmu_lock);
if (mmu_notifier_retry(vcpu, mmu_seq))
@@ -2564,6 +2556,7 @@
if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
return;
+ vcpu_clear_mmio_info(vcpu, ~0ul);
trace_kvm_mmu_audit(vcpu, AUDIT_PRE_SYNC);
if (vcpu->arch.mmu.root_level == PT64_ROOT_LEVEL) {
hpa_t root = vcpu->arch.mmu.root_hpa;
@@ -2710,7 +2703,7 @@
/* mmio */
if (is_error_pfn(pfn))
- return kvm_handle_bad_page(vcpu->kvm, gfn, pfn);
+ return kvm_handle_bad_page(vcpu, 0, 0, gfn, pfn);
spin_lock(&vcpu->kvm->mmu_lock);
if (mmu_notifier_retry(vcpu, mmu_seq))
goto out_unlock;
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 7086ca8..05310b1 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -76,4 +76,27 @@
return pte & PT_PRESENT_MASK;
}
+static inline int is_writable_pte(unsigned long pte)
+{
+ return pte & PT_WRITABLE_MASK;
+}
+
+static inline bool is_write_protection(struct kvm_vcpu *vcpu)
+{
+ return kvm_read_cr0_bits(vcpu, X86_CR0_WP);
+}
+
+static inline bool check_write_user_access(struct kvm_vcpu *vcpu,
+ bool write_fault, bool user_fault,
+ unsigned long pte)
+{
+ if (unlikely(write_fault && !is_writable_pte(pte)
+ && (user_fault || is_write_protection(vcpu))))
+ return false;
+
+ if (unlikely(user_fault && !(pte & PT_USER_MASK)))
+ return false;
+
+ return true;
+}
#endif
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 1e1c244..f0fb1a4 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -208,11 +208,8 @@
goto error;
}
- if (unlikely(write_fault && !is_writable_pte(pte)
- && (user_fault || is_write_protection(vcpu))))
- eperm = true;
-
- if (unlikely(user_fault && !(pte & PT_USER_MASK)))
+ if (!check_write_user_access(vcpu, write_fault, user_fault,
+ pte))
eperm = true;
#if PTTYPE == 64
@@ -625,8 +622,16 @@
return 0;
/* mmio */
- if (is_error_pfn(pfn))
- return kvm_handle_bad_page(vcpu->kvm, walker.gfn, pfn);
+ if (is_error_pfn(pfn)) {
+ unsigned access = walker.pte_access;
+ bool dirty = is_dirty_gpte(walker.ptes[walker.level - 1]);
+
+ if (!dirty)
+ access &= ~ACC_WRITE_MASK;
+
+ return kvm_handle_bad_page(vcpu, mmu_is_nested(vcpu) ? 0 :
+ addr, access, walker.gfn, pfn);
+ }
spin_lock(&vcpu->kvm->mmu_lock);
if (mmu_notifier_retry(vcpu, mmu_seq))
@@ -666,6 +671,8 @@
u64 *sptep;
int need_flush = 0;
+ vcpu_clear_mmio_info(vcpu, gva);
+
spin_lock(&vcpu->kvm->mmu_lock);
for_each_shadow_entry(vcpu, gva, iterator) {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a1dbd04..028a0f2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4016,6 +4016,14 @@
{
u32 access = (kvm_x86_ops->get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0;
+ if (vcpu_match_mmio_gva(vcpu, gva) &&
+ check_write_user_access(vcpu, write, access,
+ vcpu->arch.access)) {
+ *gpa = vcpu->arch.mmio_gfn << PAGE_SHIFT |
+ (gva & (PAGE_SIZE - 1));
+ return 1;
+ }
+
if (write)
access |= PFERR_WRITE_MASK;
@@ -4028,6 +4036,9 @@
if ((*gpa & PAGE_MASK) == APIC_DEFAULT_PHYS_BASE)
return 1;
+ if (vcpu_match_mmio_gpa(vcpu, *gpa))
+ return 1;
+
return 0;
}
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 256da82..d36fe23 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -75,6 +75,42 @@
return 1 << (bitno & 31);
}
+static inline void vcpu_cache_mmio_info(struct kvm_vcpu *vcpu,
+ gva_t gva, gfn_t gfn, unsigned access)
+{
+ vcpu->arch.mmio_gva = gva & PAGE_MASK;
+ vcpu->arch.access = access;
+ vcpu->arch.mmio_gfn = gfn;
+}
+
+/*
+ * Clear the mmio cache info for the given gva,
+ * specially, if gva is ~0ul, we clear all mmio cache info.
+ */
+static inline void vcpu_clear_mmio_info(struct kvm_vcpu *vcpu, gva_t gva)
+{
+ if (gva != (~0ul) && vcpu->arch.mmio_gva != (gva & PAGE_MASK))
+ return;
+
+ vcpu->arch.mmio_gva = 0;
+}
+
+static inline bool vcpu_match_mmio_gva(struct kvm_vcpu *vcpu, unsigned long gva)
+{
+ if (vcpu->arch.mmio_gva && vcpu->arch.mmio_gva == (gva & PAGE_MASK))
+ return true;
+
+ return false;
+}
+
+static inline bool vcpu_match_mmio_gpa(struct kvm_vcpu *vcpu, gpa_t gpa)
+{
+ if (vcpu->arch.mmio_gfn && vcpu->arch.mmio_gfn == gpa >> PAGE_SHIFT)
+ return true;
+
+ return false;
+}
+
void kvm_before_handle_nmi(struct kvm_vcpu *vcpu);
void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);
int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip);